hydromorphology of the econlockhatchee river
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Hydromorphology Of The Econlockhatchee River Hydromorphology Of The Econlockhatchee River
John Baker University of Central Florida
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HYDROMORPHOLOGY OF THE ECONLOCKHATCHEE RIVER
by
JOHN ALDEN BAKER, III
B.S. University of North Florida, 2010
A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Science
in the Department of Civil, Environmental, and Construction Engineering
in the College of Engineering and Computer Sciences
at the University of Central Florida
Orlando, Florida
Summer Term
2013
ii
© 2013 John Alden Baker, III
iii
ABSTRACT
Climate change and human activities alter the hydrologic systems and exerted global
scale impacts on our environment with significant implications for water resources. Climate
change can be characterized by the change of precipitation and temperature, and both
precipitation pattern change and global warming are associated with the increase in frequency of
flooding or drought and low flows. With increasing water demand from domestic, agricultural,
commercial, and industrial sectors, humans are increasingly becoming a significant component
of the hydrologic cycle. Human activities have transformed hydrologic processes at spatial
scales ranging from local to global. Human activities affecting watershed hydrology include
land use change, dam construction and reservoir operation, groundwater pumping, surface water
withdrawal, irrigation, return flow, and others.
In this thesis, the hydromorphology (i.e., the change of coupled hydrologic and human
systems) of the Econlockhatchee River (Econ River for short) is studied. Due to the growth of
the Orlando metropolitan area the Econ basin has been substantially urbanized with drastic
change of the land cover. The land use / land cover change from 1940s to 2000s has been
quantified by compiling existing land cover data and digitizing aerial photography images.
Rainfall data have been analyzed to determine the extent that climate change has affected the
river flow compared to land use change. The changes in stream flow at the annual scale and low
flows are analyzed. The Econ River has experienced minimal changes in the amount of annual
streamflow but significant changes to the amount of low flows. These changes are due to
urbanization and other human interferences.
iv
I dedicate this thesis to my loving family.
v
ACKNOWLEDGMENTS
I would like to thank my academic advisor Dr. Dingbao Wang. He has been a great
advisor, sharing ideas and concepts and teaching me how to do research. He has been an
excellent mentor throughout the entire project and I cannot thank him enough for all the
guidance and support he has given me. I would also like to thank my thesis committee members
Dr. Scott Hagen and Dr. Manoj Chopra for the support and knowledge they have shared with me.
vi
TABLE OF CONTENTS
LIST OF FIGURES ..................................................................................................................... viii
LIST OF TABLES .......................................................................................................................... x
CHAPTER 1 : INTRODUCTION .................................................................................................. 1
1.1 The Econlockhatchee River .................................................................................................. 1
1.2 Human and Climate Interferences ......................................................................................... 2
1.3 Background ........................................................................................................................... 3
1.4 Objectives .............................................................................................................................. 4
1.5 Organization of the Thesis .................................................................................................... 4
CHAPTER 2 : CLIMATE VARIABILITY AND CHANGES IN THE ECON RIVER BASIN .. 6
2.1 Precipitation .......................................................................................................................... 6
2.2 Temperature Trend .............................................................................................................. 10
2.3 Potential Evaporation Trend ................................................................................................ 12
CHAPTER 3 : HYDROLOGIC VARIABILITY AND CHANGES IN THE ECON RIVER
BASIN........................................................................................................................................... 14
3.1. Annual Stream Flow Trend ................................................................................................ 14
3.2 Annual Minimum Streamflow Trend .................................................................................. 16
3.3 Annual Maximum Streamflow Trend ................................................................................. 18
vii
3.4 Groundwater Level Trend ................................................................................................... 19
3.5 Water Balance ..................................................................................................................... 26
CHAPTER 4 HUMAN INTERFERENCES IN THE ECONLOCKHATCHEE RIVER BASIN 30
4.1 Population Growth .............................................................................................................. 30
4.2 Land Use/ Land Cover Change ........................................................................................... 31
4.3 Water Withdrawals .............................................................................................................. 58
4.4 Effluent Discharge ............................................................................................................... 61
4.5 Stormwater Management Regulations ................................................................................ 65
CHAPTER 5 : CONCLUSIONS AND FUTURE WORK ........................................................... 68
REFERENCES ............................................................................................................................. 70
viii
LIST OF FIGURES
Figure 1.1 Map of the Econlockhatchee watershed and surrounding cities. .................................. 2
Figure 2.1 Monthly precipitation of the Econ River basin. ............................................................ 8
Figure 2.2 Mean monthly rainfall for the Econ basin area. ............................................................ 9
Figure 2.3 Annual precipitation in the Econ River basin. ............................................................. 10
Figure 2.4 Monthly temperature of the Econ River basin. ........................................................... 11
Figure 2.5 Monthly potential evapotranspiration of the Econ River basin. .................................. 12
Figure 2.6 Annual evapotranspiration of the Econ River basin. ................................................... 13
Figure 3.1 Monthly flow of the Econlockhatchee River............................................................... 15
Figure 3.2 Annual streamflow of the Econ River. ........................................................................ 16
Figure 3.3 Annual minimum stream flow of the Econ River over time. ...................................... 17
Figure 3.4 Seven day annual low flow of the Econ River. ........................................................... 18
Figure 3.5 Annual maximum flow of the Econ River. ................................................................. 19
Figure 3.6 Groundwater monitoring wells in and around the Econ River watershed (shown in
blue). ............................................................................................................................................. 21
Figure 3.7 Floridan groundwater level for the Bithlo 2 Well at Bithlo. ....................................... 21
Figure 3.8 Groundwater level for the Cocoa P well near Taft. ..................................................... 22
Figure 3.9 Groundwater level for the Cocoa D well near Narcoossee. ........................................ 23
Figure 3.10 Groundwater level for the Cocoa K well. .................................................................. 24
Figure 3.11Groundwater level from the Bithlo 3 well. ................................................................. 24
Figure 3.12 Groundwater level from the Cocoa M well. .............................................................. 25
ix
Figure 3.13 E/P vs. Ep/P for the Econ watershed using a ten year moving average. ................... 28
Figure 4.1 Population growth of the Econ area over time. ........................................................... 30
Figure 4.2 1940’s Econ River basin aerial imagery map. ............................................................. 33
Figure 4.3 Land cover map of the Econ River Basin in the 1940’s. ............................................. 53
Figure 4.4 Land cover map of the Econ River Basin in 1973....................................................... 54
Figure 4.5 Land cover map of the Econ River Basin in 1995....................................................... 55
Figure 4.6 Land cover map of the Econ River Basin in 2004....................................................... 56
Figure 4.7 Water withdrawal in Orange County over time. ......................................................... 59
Figure 4.8 Water withdrawal in Seminole County over time. ...................................................... 60
Figure 4.9 Iron Bridge effluent discharge locations. .................................................................... 62
Figure.4.10 Effluent discharge from the Iron Bridge facility into the Econ River. ...................... 63
Figure 4.11 Effluent discharge into the Econ River plotted with the annual minimum flow of the
river. .............................................................................................................................................. 64
x
LIST OF TABLES
Table 2.1 Gauge stations used to piece together the Econ River climate data set. ......................... 7
Table 4.1 1973 SJRWMD land use classification table. ............................................................... 35
Table 4.2 1995 SJRWMD land use classification table. ............................................................... 38
Table 4.3 2004 SJRWMD land use classification table. ............................................................... 45
Table 4.4 Percentages of land cover over the Econ River basin. .................................................. 57
1
CHAPTER 1 : INTRODUCTION
1.1 The Econlockhatchee River
The Econlockhatchee River (Econ River for short) is located in Central Florida just east
of Orlando. The Econ River is the second largest tributary to the St. Johns River
(http://www.sjrwmd.com/middlestjohnsriver/econriver.html) and has a watershed area of roughly
705 square kilometers. Its watershed covers parts of Orange, Seminole and Osceola County.
The Econ River is made up of the Little and Big Econ Rivers. The Little Econ River is located
on the west side of the watershed and extends towards east Orlando. The mean annual
precipitation in the Econ River basin is 1,254 millimeters per year, and the mean annual flow is
roughly 292 million cubic meters (i.e., 414 millimeters) per year. Figure 1.1 below illustrates the
Econ River watershed’s location relative to Orlando and the University of Central Florida (UCF).
2
Figure 1.1 Map of the Econlockhatchee watershed and surrounding cities.
1.2 Human and Climate Interferences
The Econ River Basin has undergone substantial land use change since the 1970’s. This
land use change is the result of development and growth of the greater Orlando area. Prior to
development, the watershed was made up of wetland, forest land and upland non-forested areas.
The change in land use has impacted the flow regime of the Econ River. This thesis research
will analyze the different ways human development has impacted the Econ River.
3
Watersheds and river systems are not only affected by human development but also by
climate variations and changes. Each watershed has a different degree and frequency of
variations which is characteristic of the watershed. This thesis will investigate different climate
variables and analyze their change to evaluate how the climate variation affects the flow regime.
1.3 Background
Each watershed is unique and has different characteristics such as drainage area, location,
land use etc. Because of these characteristics there are so many complexities that can cause the
flow regime to change. Human interferences and climate change are two major attributions to
flow regime changes. In terms of flow regime changes, human interference is a general term that
means the changing of a watershed due to human practices. Human interferences can take on
many different forms such as channelization, water withdrawal, effluent discharge, land use
change, etc. The different forms of human interferences can change the flow regime in different
ways. When looking at changes in a watershed and human development it is important to
consider all the factors at hand and how they relate with one another to determine how they may
impact the watershed.
Some watersheds change due to climate change even when there is no human
interference at all. Climate variations are any fluctuations in the climate that can cause the flow
regime to change such as droughts, floods, etc. Most climates have some degree of fluctuations
throughout the year that are normal.
4
Human interferences and climate variations can interact with one another to cause
changes in flow regimes. Human interferences can amplify climate change and also minimize
climate change. Each watershed is unique and the characteristics and conditions of the
watershed should be carefully analyzed to determine what factors are involved in changes to the
flow regime.
1.4 Objectives
Below are the research objectives of this case study of the Econ River.
I. Analyze and quantify trends in the climate that relate to the Econ River flow regime.
II. Analyze and quantify land use change over time.
III. Analyze other human interferences such as groundwater pumping, effluent discharge, and
storm water management practices.
IV. Discuss the relationship between human and climate interferences and how they relate to
the flow regime change in the Econ River basin.
1.5 Organization of the Thesis
This thesis is broken down into 5 chapters to provide the framework of the research goals.
Chapter 1: Introduction – This chapter contains the abstract as well as base information
about the Econlockhatchee River basin. Also discussed are the general concepts of
human and climate interferences and how they can affect watersheds.
5
Chapter 2: Climate variability and changes in the Econ River basin – This chapter
explains methods used to analyze climate data for the Econ River basin.
Chapter 3: Hydrologic changes and variability in the Econ River basin – This chapter
presents methods used to analyze stream flow data and groundwater data for the Econ
River basin. Findings and results are discussed to determine common trends.
Chapter 4: Human interferences in the Econ River basin – This chapter presents methods
used to analyze land use, population and water withdrawal data. Storm water regulations
and effluent discharge are explored to determine relationships with streamflow analyses.
Chapter 5: Conclusions and future work – Overall conclusions are summarized and
presented. Recommendations of future work and analyses are discussed.
6
CHAPTER 2 : CLIMATE VARIABILITY AND CHANGES IN THE ECON
RIVER BASIN
The Econ River basin is located in a subtropical climate. The summers are hot and
humid and winters are mild and warm. The climate aridity index (Ep/P) is 0.93. The average
precipitation is 1,254 millimeters per year. During the summer afternoon thunderstorms are
frequent and regular. Many northerners come down for the winter every year to enjoy the
warmer temperatures and plentiful sunshine.
2.1 Precipitation
There are many different factors in a water balance for a watershed. Precipitation is one
of the most important factors because it is the main input into the system. Precipitation
recharges the aquifers, provides water sources for evaporation and produces runoff that turns into
stream flow. Fluctuation in precipitation can significantly change the stream flow over time.
Different climate systems have different rainfall patterns and volumes over time. The stream
flow in the Econ watershed is greatly made up of runoff and the discharge of shallow aquifers.
Both of which are directly affected by the amount of precipitation.
Data was gathered from several rain stations around the Econ River basin vicinity to
compile rain data dating as far back as the 1940’s. Data was gathered from NOAA National
Climatic Data Center of (http://www.ncdc.noaa.gov/cdo-web/) . This data was pieced together
since there was no one rain station that had a complete data set that covered the study period
without significant gaps in the data.
7
Table 2.1 Gauge stations used to piece together the Econ River climate data set.
Climate Data
Year Station Name Station ID
1/1/1940-12/31/1952 Lake Hiawassee 84771
1/1/1953-2/1/1959 Orlando Int. Airport 86628
2/2/1959 - 12/31/1963 Bithlo 80758
1/1/1964 - 12/31/1970 Orlando Int. Airport 86628
1/1/1971 - 1/31/1974 Bithlo 80758
2/1/1974 - 10/31/2010 Orlando Int. Airport 86628
Although precipitation does vary in different areas, it was determined in the case of this study
that piecing together a data set was acceptable to gather a large enough data set and get a general
idea of the annual rainfall trends in the area. Table2.1 shows the different gauge stations that
were used and the time period of the data that was used. Looking at annual values of long time
periods help to determine drought periods and periods of abnormal precipitation amounts.
8
Figure 2.1 Monthly precipitation of the Econ River basin.
The monthly precipitation is the total precipitation of the month divided by the number of
days in that month. Figure 2.1 show the mean monthly precipitation of each month plotted out
over time. Each year there are dry seasons and rainy seasons which cause the graph to move up
and down. The peaks vary greatly from year to year with some years the highest monthly
average reaching nearly 16 mm/day. Overall there does not appear to be a significant increase
over time in the mean monthly precipitation.
y = 5E-06x + 3.2953 R² = 0.0002
0
2
4
6
8
10
12
14
16
Jan
-40
Sep
-42
May
-45
Jan
-48
Sep
-50
May
-53
Jan
-56
Sep
-58
May
-61
Jan
-64
Sep
-66
May
-69
Jan
-72
Sep
-74
May
-77
Jan
-80
Sep
-82
May
-85
Jan
-88
Sep
-90
May
-93
Jan
-96
Sep
-98
May
-01
Jan
-04
Sep
-06
May
-09
Pre
cip
itat
ion
(m
m/d
ay)
Time
Monthly Precipitation
9
Figure 2.2 Mean monthly rainfall for the Econ basin area.
Figure 2.2 show the average rainfall for the different months of the year for the Econ
watershed. The wet season is June through September which shows a monthly rainfall total of
160 mm to about 190 mm. The other months of the year have totals between 50 mm to just over
80 mm.
0
20
40
60
80
100
120
140
160
180
200
Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec
mm
/mo
nth
Month
Precipitation
10
Figure 2.3 Annual precipitation in the Econ River basin.
Figure 2.3 shows the annual precipitation and runoff for the Econ river basin. There are
many peaks and valleys for the precipitation and the peak years can differ from the drought years
by almost five hundred millimeters. The average precipitation rate is 1254 mm per year.
2.2 Temperature Trend
Temperature variations in a watershed are indicators of drought and high amounts of
evaporation. Generally high temperatures result in an increased amount of evaporation.
y = 0.7673x + 1227 R² = 0.0052
700
900
1100
1300
1500
1700
1900
19
40
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92
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96
20
00
20
04
20
08
mm
Year
Annual Precipitation
Precipitation
Linear (Precipitation)
11
Figure 2.4 Monthly temperature of the Econ River basin.
The mean monthly temperature varies from month to month depending on the time of year.
Figure 2.4 shows the mean monthly temperatures over time. There is a regular cycle as the
seasons progress throughout the year. Peak times are during the summer and average around
82.5 degrees and the lows during the winter averaging around 60 degrees. There does not appear
to be any significant overall trend although the trend line shows a slight increasing trend.
y = 6E-05x + 70.797 R² = 0.0025
50
55
60
65
70
75
80
85
90
Jan
-40
Sep
-42
May
-45
Jan
-48
Sep
-50
May
-53
Jan
-56
Sep
-58
May
-61
Jan
-64
Sep
-66
May
-69
Jan
-72
Sep
-74
May
-77
Jan
-80
Sep
-82
May
-85
Jan
-88
Sep
-90
May
-93
Jan
-96
Sep
-98
May
-01
Jan
-04
Sep
-06
May
-09
Tem
pe
ratu
re (
Fah
ren
he
it)
Time
Monthly Temperature
12
2.3 Potential Evaporation Trend
Figure 2.5 Monthly potential evapotranspiration of the Econ River basin.
The mean monthly evapotranspiration follows the trend of the mean monthly
temperature. The graph is very cyclical because of the time of year. The peaks average around 5
mm per day and the valleys average just over 1mm per day. There is a slight increasing trend that
follows the trend of the temperature.
y = 6E-06x + 2.917 R² = 0.0012
0
1
2
3
4
5
6
Jan
-40
Au
g-4
2
Mar
-45
Oct
-47
May
-50
De
c-5
2
Jul-
55
Feb
-58
Sep
-60
Ap
r-6
3
No
v-6
5
Jun
-68
Jan
-71
Au
g-7
3
Mar
-76
Oct
-78
May
-81
De
c-8
3
Jul-
86
Feb
-89
Sep
-91
Ap
r-9
4
No
v-9
6
Jun
-99
Jan
-02
Au
g-0
4
Mar
-07
Oct
-09
Ep (
mm
)
Time
Monthly Ep
13
Figure 2.6 Annual evapotranspiration of the Econ River basin.
Figure 2.6 shows the total evapotranspiration per year over time. The figure shows many
peaks and valleys over time. There is one drop from about 1962 to about 1970. This drop was
most likely caused by a stretch of slightly colder temperatures. Overall, the figure shows an
increasing trend. This dramatic increasing trend follows the very slight increasing trend of the
temperature.
y = 0.6773x + 1103 R² = 0.2317
10251045106510851105112511451165118512051225
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40
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96
20
00
20
04
20
08
Ep (
mm
)
Time (Year)
Annual Ep
Annual Ep
Linear (Annual Ep)
14
CHAPTER 3 : HYDROLOGIC VARIABILITY AND CHANGES IN THE
ECON RIVER BASIN
This chapter will discuss the hydrologic variability and changes of the Econ River basin
over time. The Econ River basin has been developed, had substantial land use change and
population growth since 1960s. These changes have induced change of hydrologic regimes in
the Econ River and groundwater table. This chapter will analyze the changes in the flow regime
and explain the methods used to determine the changes.
3.1. Annual Stream Flow Trend
Data was gathered from the USGS website of
(http://waterdata.usgs.gov/fl/nwis/nwisman/?site_no=02233500/). The stream flow data at the
gauge station located in Chuluota (gauge number is 02233500) is downloaded. The streamflow
data ranges from 1940 to 2009. This long period of time is needed to determine any changes
from its natural state. During the 1940’s the population was small in the watershed which means
the human interferences to the streamflow was at a minimum. It will be shown that the
increasing population over the years has changed the water cycle in the Econ River basin.
15
Figure 3.1 Monthly flow of the Econlockhatchee River
Figure 3.1 shows the monthly stream flow of the Econ River over the past 70 years.
There are distinct peaks across the figure. From about 1965 to 2003 the peaks are less than 6
mm/day. This may be due to a drought or some type of water management flood control. There
are only two peaks after 2003 that are about 6 mm/day. These peaks can be attributed to
hurricane Charley (2004) and Tropical Storm Fay (2008). The low flow has a somewhat
noticeable increase over time. This is also indicated by the trend line that shows a positive
increase.
y = 1E-05x + 0.8659 R² = 0.0031
0
1
2
3
4
5
6
7
8
9
Jan
-40
Au
g-4
2
Mar
-45
Oct
-47
May
-50
De
c-5
2
Jul-
55
Feb
-58
Sep
-60
Ap
r-6
3
No
v-6
5
Jun
-68
Jan
-71
Au
g-7
3
Mar
-76
Oct
-78
May
-81
De
c-8
3
Jul-
86
Feb
-89
Sep
-91
Ap
r-9
4
No
v-9
6
Jun
-99
Jan
-02
Au
g-0
4
Mar
-07
Oct
-09
Flo
w (
mm
/day
)
Time
Monthly Flow
16
Figure 3.2 Annual streamflow of the Econ River.
Figure 3.2 shows the annual streamflow of the Econ River over time. The trend line
shows a slight increase over time. The increase in annual streamflow is most likely caused by
increased development and impervious surface over the basin. There are far fewer low valleys
after 1981. This indicates an increasing low flow which corresponds to Figure 3.1 of the
monthly flow. There was a spike in 1960 that was a result of a large increase in rainfall that
caused extreme flooding throughout Florida.
3.2 Annual Minimum Streamflow Trend
The minimum streamflow of the Econ River is mostly made up of base flow from the
recession event. This is when water is released from the shallow aquifer into the river. Human
interferences that could cause the low flow to change such as effluent discharge, water
y = 1.2711x + 368.75 R² = 0.0203
0
200
400
600
800
1000
1200
19
40
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44
19
48
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52
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56
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60
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84
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96
20
00
20
04
20
08
mm
/ye
ar
Year
Annual Streamflow
Streamflow
Linear (Streamflow)
17
withdrawal, and water storage. Using the streamflow data the annual minimum flows were
determined for each year and plotted.
Figure 3.3 Annual minimum stream flow of the Econ River over time.
Figure 3.3 above shows an increasing annual minimum stream flow for the Econ River
over time. This increase is most likely due to some type of human interference. Increasing
population and increasing development are two factors that can cause the increase in the low
flow.
1936 1946 1956 1966 1976 1986 1996 2006
10-1
Year
Ann
ual
Min
. Q
(m
m d
-1)
18
Figure 3.4 Seven day annual low flow of the Econ River.
Figure 3.4 shows the seven day low flow for two different gauge stations on the Econ
River. The blue represents USGS gauge number 02233200, which measures the flow for the
Little Econ River. The red represents the USGS gauge number 02233500, which measures the
flow for the entire Econ River. Both stations show an increasing low flow. The Little Econ
River gauge shows slightly higher increases. This could be due to the fact that the percentage of
development in that basin was greater compared to the percentage of development in the entire
Econ River basin.
3.3 Annual Maximum Streamflow Trend
The annual maximum streamflow is the maximum streamflow each year plotted over
time. Looking at the annual maximum streamflow can give indications of human interferences
or increased precipitation events. Maximum streamflow is caused by large precipitation events
1930 1940 1950 1960 1970 1980 1990 2000 20100
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Year
7-d
ay a
nn
ua
l lo
w f
low
(m
m d
-1)
19
and the runoff due to the large volume of precipitation. Channelization is a type of human
interference that can cause the annual maximum streamflow to increase because it can convey
more runoff into the river which will increase the streamflow. Human interference can also
cause a decrease in maximum streamflow because of stormwater ponds holding back flood
waters to release them at a later time after the storm event has past.
Figure 3.5 Annual maximum flow of the Econ River.
Figure 3.5 shows the annual maximum flow for the river over time. The figure has many
peaks and valleys. There appears to be no overall trend in the annual maximum flow. There are
a few valleys after 1976 that can be attributed to drought years during that time.
3.4 Groundwater Level Trend
The groundwater is an important aspect of a watershed and its streamflow. Land use
change and climate change can both cause changes in groundwater quantity which can affect the
1936 1946 1956 1966 1976 1986 1996 200610
0
101
102
Year
Ann
ual
Max.
Q (
mm
d-1
)
20
low flow of the river. Groundwater is a natural resource that is very important because it is a
primary source of potable water for the Central Florida population.
The Florida aquifer is a confined aquifer deep underground that covers large areas of
Florida. The depth and confinement of this aquifer make it much more resistant to drought. The
Florida aquifer is not directly connected to the Econ River. This aquifer is recharged through
infiltration of the surficial aquifer or recharge zones.
Surficial aquifers are shallow and may be directly connected to the Econ River. These
types of aquifers are greatly influenced by precipitation patterns and human interferences.
Channelization and large amounts of impervious areas decrease infiltration rates and can affect
the water level in surficial aquifers.
Groundwater levels around the Econ River basin were analyzed to better understand the
interactions between the groundwater and the flow regime. Figure 3.6 shows a map of a few of
the groundwater monitoring wells that were analyzed. When determining which well to analyze
it was important to find wells that were near the watershed and also had a substantial time period.
Six wells were chosen that had data from the late 60’s to early 70’s.
21
Figure 3.6 Groundwater monitoring wells in and around the Econ River watershed (shown in
blue).
Figure 3.7 Floridan groundwater level for the Bithlo 2 Well at Bithlo.
y = -0.0004x + 62.501
40
45
50
55
60
6/11/1968 12/2/1973 5/25/197911/14/1984 5/7/1990 10/28/19954/19/200110/10/2006 4/1/2012Ele
vati
on
ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Bithlo 2 (Intermediate)
22
The Bithlo 2 Well at Bithlo is from USGS gauge number 283249081053202 (
http://nwis.waterdata.usgs.gov/fl/nwis/dv/?site_no=283249081053202&agency_cd=USGS&
;referred_module=gw). This well is a 75 foot deep well located on the east side of the Econ
basin. Figure 3.7 shows the elevation of the water in the well over time. There is a clear decrease
in elevation over time from the late 70’s on.
Figure 3.8 Groundwater level for the Cocoa P well near Taft.
The Cocoa P well near Taft is from USGS gauge 282623081153801.
http://nwis.waterdata.usgs.gov/fl/nwis/dv/?site_no=282623081153801&agency_cd=USGS&
;referred_module=gw This well is 439 feet deep and located on the south side of the Little Econ
River watershed. Figure 3.8 shows the water level in the well over time. There appears to be a
decreasing trend from around 1995 on. There are some low valleys that could be due to ground
water pumping in the area. This well is very deep and in the Florida aquifer system.
y = -0.0004x + 57.322
30
35
40
45
50
55
8/20/1970 2/10/1976 8/2/1981 1/23/1987 7/15/1992 1/5/1998 6/28/2003 12/18/2008Ele
vati
on
ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Cocoa P (Floridan)
23
Figure 3.9 Groundwater level for the Cocoa D well near Narcoossee.
The Cocoa D well near Narcoossee is from USGS gauge 282531081095701.
http://nwis.waterdata.usgs.gov/fl/nwis/dv/?site_no=282531081095701&agency_cd=USGS&
;referred_module=gw This well is 300 feet deep and located on the west side of the Econ River
watershed. Figure 3.9 shows the water level in the well over time. There appears to be a
significant decreasing trend. This well is also in the Florida aquifer system.
y = -0.0004x + 48.544
25
30
35
40
45
9/15/1965 3/8/1971 8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009Ele
vati
on
ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Cocoa D (Floridan)
24
Figure 3.10 Groundwater level for the Cocoa K well.
The Cocoa K well is from the USGS gauge 282847081013702.
http://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=282847081013702
This well is 8 feet deep and located just east of the Econ River watershed. There appears to be a
slight decreasing trend over time. This well is located in the surficial aquifer system.
Figure 3.11Groundwater level from the Bithlo 3 well.
y = -4E-05x + 58.956
53
54
55
56
57
58
59
60
61
8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009Ele
vati
on
ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Cocoa K (Surficial)
y = -0.0002x + 66.697
52
54
56
58
60
62
64
10/24/1969 4/16/1975 10/6/1980 3/29/1986 9/19/1991 3/11/1997 9/1/2002 2/22/2008Ele
vati
on
ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Bithlo 3 (Surficial)
25
The Bithlo 3 well is from the USGS gauge 283249081053203.
http://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=283249081053203
This well is 15 feet deep and located on the east side of the watershed near Bithlo. This figure
shows a decrease over time starting from the mid 80’s. There are large valleys that may be the
result of droughts compounded by human impacts. This well is located in the surficial aquifer
system.
Figure 3.12 Groundwater level from the Cocoa M well.
The Cocoa M well is from the USGS gauge 282510081054502.
http://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=282510081054502
This well is 10 feet deep and located on the south end of the Econ River watershed. This figure
shows a few low levels but overall no significant trend. This well is also located in the surficial
aquifer system. The southern end of the watershed is relatively untouched which is most likely
why we do not see any significant changes.
y = -1E-05x + 66.514
59
61
63
65
67
69
71
12/2/1973 5/25/1979 11/14/1984 5/7/1990 10/28/1995 4/19/2001 10/10/2006 4/1/2012Wat
er
leve
l ab
ove
NG
VD
29
(ft
)
Date
Groundwater Level - Cocoa M (Surficial)
26
Of the six wells presented most show a slight decrease over time. The well that does not
show a decrease is located in the most undeveloped portion of the watershed. This indicates that
the human impacts likely have decreased the groundwater levels. Since the low flow of the Econ
River is largely controlled by the surficial aquifer levels. It is important to look at those wells
separately from the Florida aquifer wells. Two of the three surficial aquifer wells show a
decrease over time. As stated above the third well likely shows no decrease since it is located in
a relatively untouched area of the watershed. Although the wells show a decrease over time the
low flow shows an increase over time. Typically lower surficial groundwater levels will lower
the low flow because the relative flow into the river from the aquifer will be less. In this case the
opposite has happened. This is most likely due to other human impacts that can increase the low
flow such as effluent discharge and stormwater management regulations. These characteristics
will be discussed in chapter 4.
3.5 Water Balance
When looking at the hydrologic changes in a watershed it is important analyze the entire
water balance to understand any changes. Changes in the climate can affect streamflow as can
human interferences. One way to look at the differences is using the Budyko method. The
Budyko method is a conceptual method that can be used to determine if changes are climate
impacts or human impacts or both. Budyko determined that the mean annual evaporation can be
calculated using the mean annual precipitation and potential evaporation. The Budyko method
assumes that the change in storage is negligible over a long period of time. For our case study
27
the annual precipitation data and annual runoff data were used to determine the evaporation
(E=P-Q). This method assumes that for each year the excess precipitation that is not runoff is
evaporation. In other words there is no change of storage and all precipitation is evaporated or
runoff into the stream. This allows for the determination of the evaporation ratio at an annual
scale.
The temperature data was used to calculate the potential evaporation using the Hamon
method. Temperature data that was compiled using the same gauges as the precipitation data.
These gauges consisted of daily minimum and maximum temperature values. The values were
averaged together to determine the average temperature for each day over the entire data set.
Along with the latitude, these temperatures were used in the Hamon method to calculate the
evapotranspiration each day of the data set.
In order to look more at long term averages a 10 year moving average was calculated
using mean annual values of precipitation, evaporation and potential evaporation. This helps to
reduce the effects of short term droughts and other anomalies. The dryness index (Ep/P) and the
evaporation ratio (E/P) were calculated. Budyko proposed that the points would move along the
curve if there were no human impacts on the system. If the climate became drier, the subsequent
evaporation ratio would adjust as well and this change would follow the Budyko curve.
28
Figure 3.13 E/P vs. Ep/P for the Econ watershed using a ten year moving average.
Figure 3.13 shows the 10 year moving average of the Econ Watershed plotted along with
the Budyko curve. In this figure the 1944 – 1970 values and the 1982-2004 values are along the
Budyko curve and the 1971-1981 values are above the curve. The values from 1944 to 1970
reflect a time in the watershed where there were relatively no human interferences. As proposed
by the Budyko method the values fall along the curve. The values from 1971 – 1981 are above
the curve showing that there is some sort of human interferences during this time that have
altered the evaporation ratio relative to the climatic dryness index. This time period is right
around the start of major development in the Greater Orlando area which is most likely the cause
0.6
0.62
0.64
0.66
0.68
0.7
0.72
0.74
0.76
0.78
0.8
0.8 0.82 0.84 0.86 0.88 0.9 0.92 0.94 0.96 0.98 1
E/P
Ep/P
Econ Watershed (10yr Moving Average)
1944-1970
1971-1981
1982-2004
Budyko Curve
29
of the variation. In the years 1982 to 2004 the values fall back on the Budyko curve. Although
the values fall along the curve it does not mean that the watershed has been restored to its natural
state. In contrast we will see in chapter 4 that the watershed is further developed over time. The
reason the points fall back along the curve is most likely due to a human interference that has
changed the flow regime to counter act previous interferences. Examples of this may be
stormwater management practices changing the way development deals with stormwater.
Another example may be the development of a regional water treatment facility. Both of these
examples can change a flow regime and the values plotted along the Budyko curve.
30
CHAPTER 4 HUMAN INTERFERENCES IN THE
ECONLOCKHATCHEE RIVER BASIN
4.1 Population Growth
Population growth in an area is an indicator of human interferences such as water
withdrawal, channelization, effluent discharge and others. These types of human interferences
can affect the water cycle in different ways depending on the watershed properties. Substantial
population in a short time period will most likely change the watershed in a significant way.
Figure 4.1 Population growth of the Econ area over time.
The population growth for the Econ River basin can be generally determined by looking at the
population growth of the counties the watershed is located in. Figure 4.1 shows the population
growth over time in the Orange and Seminole counties. This figure shows the population in the
0
200
400
600
800
1000
1200
1960 1970 1980 1990 2000 2010
Po
pu
lati
on
(th
ou
san
d)
Year
Population Growth of the Econlockhatchee Area
Orange…Seminole…
31
Orange and Seminole counties nearly triples from 1970 to 2010. This growth from the Orlando
area indicates that the Econ River Basin has some significant human interferences.
4.2 Land Use/ Land Cover Change
The Econ River basin has had significant changes in land use and land cover. Prior to the
1970’s the basin was primarily made up of upland non-forested and wetland areas, since then
significant parts of the basin have been paved and developed. This section will focus on the land
use change over time and what methods were used to gather this data.
When looking at a basin to see how human interferences have affected it, it is important
to gather a base point of what the basin was like before there was substantial human
development. Land use and land cover data is not widely available before the 1970’s. To
determine the land cover at the basin’s natural state, aerial imageries from the 1940’s were
digitized and geo-referenced in the software of ArcGIS to determine general percentages of the
different types of land cover. The aerial imageries were gathered from the University of
Florida’s historical imagery department. The hard copy of the images were scanned and
digitized and then made available on the University of Florida’s historical imagery website
(ufdc.ufl.edu/aerials). On the website each flight had meta-data available which gave the latitude
and longitude of each image. Due to the size of the Econ River basin there was not one flight
that contained all the images that covered the entire basin. Multiple flights from different years
in the 1940’s were used to piece together an image of the basin during that time. These images
were geo-referenced into ArcGIS by importing each image separately. Once the image was on
32
the map it was placed in the correct location using the ArcGIS georeferencing tool. This tool
allows images to be referenced using a point and assigning the latitude and longitude for each
corner of the image. Since the images were scanned most of the images edges were out of focus.
This made the corners of the images difficult to pick and assign the correct coordinates to. For
the purposes of this project assigning the coordinates to the best guess of the corner of the
images was determined to be acceptable. This procedure places the images in the most accurate
location possible. Once all the images were geo-referenced into ArcGIS they were aggregated
together to form a composite image of the basin.
33
Figure 4.2 1940’s Econ River basin aerial imagery map.
34
Although multiple flights were used during the 1940’s there were not enough images to
cover the entire Econ River basin. Enough imagery was gathered to cover about 84% of the
basin. It was determined this was enough coverage to give a general picture of what the basin
was like during the 1940’s. The image was then digitized by creating 6 different categories.
The categories that were made were upland non-forested, forest, wetland, water, agricultural, and
urban. These categories were digitized using ArcGIS. A layer was made for each land cover
category. Each layer was then used to trace out the different land cover on the map by using the
ArcGIS layer editing tools. Polygons were roughly drawn over the associated land type. Once
the layers were saved they could then be used to determine the areas and percentages.
Additional maps were made to look at the Econ River basin and how it changes over
time. These maps were made using data from the St. Johns River Water Management District
(http://www.sjrwmd.com/gisdevelopment/docs/themes.html). The data for this area was
available for the years 1973, 1995 and 2004. This data consisted of many detailed land use / land
cover classifications.
For the purposes of this project it was determined it was better to generalize the data into
9 categories, Urban, Industrial, Recreational, Transportation & Utilities, Agricultural, Water,
Wetland, Forest, and Upland Non-forested. These categories were made to better understand the
general land uses and compare them with the 1940’s map. See table 4.1, 4.2 and 4.3 for the land
use / land cover classifications and how they were more generally categorized.
35
Table 4.1 1973 SJRWMD land use classification table.
1973 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Upland Non-
Forested
0 No Data
1 Open Land
18 Clear-cut Areas
20 Grassy Scrub
21 Sand Pine Scrub
22 Sandhill Communities
23 Pine Flatwood
24 Xeric Hammock
Recreation 2 Recreation
Urban
3 Residential Low-Density
4 Residential Medium Density
5 Residential High Density
8 Commercial & Service
Industrial
6 Industrial
7 Mining
9 Institutional
36 Borrow Pit
42 Spoil Bank
36
1973 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Transportation,
Communications &
Utilities
10 Transportation
11 Utilities & Communications
Agriculture
12 Improved Pasture
13 Cropland
14 Citrus Groves
15 Nurseries & Special Crops
16 Confined Feeding
17 Planted Pine
19 Agriculture Other
Forest
25 Mesic Hammock
29 Cypress Dome
Wetlands
26 Hydric Hammock
27 Hardwood Swamp (Riverine)
28 Riverine Cypress
30 Bayheads & Bogs
31 Wet Prairies
32 Fresh Water Marsh
37 Tidal Flat
40 Salt Marsh
37
1973 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Wetlands
41 Mangroves
43 M. Salt Plankton Estuary
44 Oligohaline System
45 Neutral Embayment
46 Marine Meadow
47 Costal Plankton
Water
33 Rivers
34 Lakes & Ponds
35 Reservoir
48 High Velocity Channel
38
Table 4.2 1995 SJRWMD land use classification table.
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Upland Non-
Forested
3100 Herbaceous
3200 Shrub and Brushland
3300 Mixed Rangeland
4100 Upland Coniferous Forests
4110 Pine Flatwoods
7100 Beaches Other Than Swimming Beaches
7200 Sand Other Than Beaches
7300 Exposed Rocks
7400 Disturbed Land
7410
Rural Land in Transition without Positive Indicators of
Intended Activity
7420 Borrow Areas
7430 Spoil Areas
Recreation
1810 Swimming Beach
1820 Golf Course
1830 Race Tracks
1840 Marinas and Fish Camps
1850 Parks and Zoos
1870
Stadiums: Those Facilities Not Associated with High
Schools, Colleges or Universities
39
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Urban
1100
Residential, Low Density - Less than two dwelling units per
acre
1200
Residential, Med. Density - Two to five dwelling units per
acre
1300 Residential, High Density
1400
Commercial and Services. Condominiums and Motels
combined.
1460
Oil and gas storage: except those areas associated with
industrial use or manufacturing
1480 Cemeteries
1920 Inactive land with street pattern but without structures
Industrial
1510 Food Processing
1520 Timber Processing
1523 Pulp and Paper Mills
1530 Mineral Processing
1540 Oil and Gas Processing
1550 Other light Industry
1560 Other heavy Industrial
1561 Ship building and repair
1562 Prestressed concrete plants
1563 Metal Fabrication Plants
40
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Industrial
1610 Strip Mines
1611 Clays
1612 Peat
1613 Heavy Metals
1620 Sand and Gravel Pits
1630 Rock Quarries
1632 Limerock or Dolomite
1633 Phosphates
1634 Heavy Minerals
1640 Oil and Gas Fields
1650 Reclaimed Lands
1660 Holding Ponds
1670 Abandoned Lands
1730 Military
1750 Governmental
Transportation,
Communications &
Utilities
8100 Transportation
8110 Airports
8120 Railroads
8130 Bus and Truck Terminals
8140 Roads and Highways
8150 Port Facilities
41
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Transportation,
Communications &
Utilities
8160 Canals and Locks
8180
Auto Parking Facilities - when not directly related to other
land uses
8190 Transportation Facilities Under Construction
8191 Highways
8192 Railroads
8193 Airports
8194 Port Facilities
8200 Communications
8300 Utilities
8310 Electrical Power Facilities
8320 Electrical Power Transmission Lines
8330 Water Supply Plants
8340 Sewage Treatment Plants
8350 Solid Waste Disposal
8360 Treatment Ponds (Non-Sewage)
8390 Utilities Under Construction
Agriculture
2100 Cropland and Pastureland
2110 Improved Pastures
2120 Unimproved Pastures
2130 Woodland Pastures
42
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Agriculture
2140 Row Crops
2141 Potatoes and Cabbage
2150 Field Crops
2160 Mixed Crops: Used if crop type cannot be determined
2200 Tree Crops
2210 Citrus Groves
2240 Abandoned Tree Crops
2300 Feeding Operations
2310 Cattle Feeding Operations
2320 Poultry Feeding Operations
2400 Nurseries and Vineyards
2410 Tree Nurseries
2430 Ornamentals
2431 Shade Ferns
2432 Hammock Ferns
2450 Floriculture
2500 Specialty Farms
2510 Horse Farms
2520 Dairies
2540 Aquaculture
2600 Other open lands - Rural
43
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Agriculture 2610 Fallow Cropland
Forest
4120 Longleaf Pine - Xeric Oak
4130 Sand Pine
4200 Upland Hardwood Forest (4200 - 4399)
4210 Xeric Oak
4300 Upland Mixed Forest
4340 Upland Mixed Coniferous/Hardwood
4370 Australian Pine
4400 Tree Plantations
4410 Coniferous Pine
4430 Forest Regeneration
Wetlands
6100 Wetland Hardwood Forests
6110 Bay Swamps
6120 Mangrove Swamps
6150 River/Lake Swamp (bottomland)
6170 Mixed Wetland Hardwoods
6180 Cabbage Palm Savanna
6200 Coniferous Forest
6210 Cypress
6220 Forested Depressional Pine
6300 Wetland Forested Mixed
44
1995 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Wetlands
6400 Vegetated Non-Forested Wetlands
6410 Freshwater Marshes
6420 Saltwater Marshes
6430 Wet Prairies
6440 Emergent Aquatic Vegetation
6450 Submergent Aquatic Vegetation
6460 Mixed Scrub-Shrub Wetland
Water
5100 Streams and Waterways
5200 Lakes
5300 Reservoirs
5340
Reservoirs Less than 10 Acres (4 hectares) which are
Dominant Features
5400 Bays and Estuaries
5500 Major Springs
5600 Slough Waters
45
Table 4.3 2004 SJRWMD land use classification table.
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Upland Non-
Forested
1900 There are none
2600 Other Open Lands - Rural
3100 Herbaceous Upland Nonforested
3200 Shurb and Brushland
3300 Mixed Upand Nonforested
4110 Pine Flatwoods
7100 Beaches other than Swimming Beaches
7200 Sand other than Beaches
7400 Disturbed Land
7410
Rural Land in Transition without positive indicators of
intended activity
7420 Borrow Areas
7430 Spoil Areas
Recreation
1800 Recreational
1810 Swimming Beach
1820 Golf Course
1830 Race Tracks
1840 Marinas and Fish Camps
46
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Recreation
1850 Parks and Zoos
1860 Community Recreational Facilities
1870
Stadiums: Those facilities not associated with High
Schools, Colleges or Universities
1890 Other Recreational
Urban
1100
Residential, Low Density - Less than 2 dwelling units per
acre
1180
Residential, Rural - Less than or equal to 0.5 dwelling units
per acre (one unit on 2 or more acres)
1190 Low Density under Construction
1200
Residential, Med. Density - Two to five dwelling units per
acre
1290 Medium Density under Construction
1300 Residential, High Density
1390 High Density under construction
1400 Commercial and Services
1460
Oil and gas storage: except those areas associated with
Industrial use or Manufacturing
1480 Cemeteries
1490 Commercial and Services under Construction
1920 Inactive Land with Street Pattern but without structures
47
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Industrial
1510 Food Processing
1520 Timber Processing
1523 Pulp and Paper Mills
1530 Mineral Processing
1540 Oil and Gas Processing
1550 Other Light Industry
1560 Other Heavy Industrial
1561 Ship Building and Repair
1562 Prestressed Concrete Plants
1563 Metal Fabrication Plants
1590 Industrial Under Construction
1600 Extractive
1610 Strip Mines
1611 Clays
1612 Peat
1613 Heavy Metals
1620 Sand and Gravel Pits
1630 Rock Quarries
1632 Limerock or Dolomite
1633 Phosphates
1640 Oil and Gas Fields
48
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Industrial
1650 Reclaimed Lands
1670 Abandoned Mining Lands
1700 Institutional
1730 Military
1750 Governmental ( to be used for KSC only)
Transportation,
Communications &
Utilities
8100 Transportation
8110 Airports
8120 Railroads
8130 Bus and Truck Terminals
8140 Roads and Highways
8150 Port Facilities
8180
Auto Parking Facilities - when not directly related to other
land uses
8190 Transportation Under Construction
8200 Communications
8290 Communications Under Construction
8300 Utilities
8310 Electrical Power Facilities
8320 Electrical Power Transmission Lines
8330 Water Supply Plants
8340 Sewage Treatment Plants
49
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Transportation,
Communications &
Utilities
8350 Solid Waste Disposal
8390 Utilities Under Construction
Agriculture
2110 Improved Pastures
2120 Unimproved Pastures
2130 Woodland Pastures
2140 Row Crops
2143 Potatoes and Cabbage
2150 Field Crops
2160 Mixed Crops
2200 Tree Crops
2210 Citrus Groves
2240 Abandoned Tree Crops
2300 Feeding Operations
2310 Cattle Feeding Operations
2320 Poultry Feeding Operations
2400 Nurseries and Vineyards
2410 Tree Nurseries
2420 Sod Farms
2430 Ornamentals
2431 Shade Ferns
50
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Agriculture
2432 Hammock Ferns
2450 Floriculture
2500 Specialty Farms
2510 Horse Farms
2520 Dairies
2540 Aquaculture
2610 Fallow Cropland
Forest
4120 Longleaf Pine - Xeric Oak
4130 Sand Pine
4200 Upland Hardwood Forest
4210 Xeric Oak
4280 Cabbage Palm
4300 Upland Mixed Forest
4340 Upland Mixed Coniferous/Hardwood
4370 Australian Pine
4400 Tree Plantations
4410 Coniferous Pine
4430 Forest Regeneration
Wetlands
6100 Wetland Hardwood Forests
6110 Bay Swamps
6120 Mangrove Swamp
51
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Wetlands
6170 Mixed Wetland Hardwoods
6180 Cabbage Palm Wetland
6181 Cabbage Palm Hammock
6182 Cabbage Palm Savannah
6200 Wetland Coniferous Forest
6210 Cypress
6220 Pond Pine
6250 Hydric Pine Flatwoods
6300 Wetland Forested Mixed
6400 Vegetated Non-Forested Wetlands
6410 Freshwater Marshes
6420 Saltwater Marshes
6430 Wet Prairies
6440 Emergent Aquatic-Vegetation
6460 Mixed Scrub-Shrub Wetland
6500 Non-Vegetated Wetland
Water
1660 Holding Ponds
5100 Streams and Waterways
5200 Lakes
5250 Marshy Lakes
5300 Reservoirs
52
2004 SJRWMD Land Use Data
General
Classification
SJRWMD Classification
Land Use
Code Description
Water
5400 Bays and Estuaries
5430 Enclosed Saltwater Ponds within a Salt Marsh
5500 Major Springs
5600 Slough Waters
8160 Canals and Locks
8360 Other Treatment Ponds
8370 Surface Water Collection Basin
53
Figure 4.3 Land cover map of the Econ River Basin in the 1940’s.
54
Figure 4.4 Land cover map of the Econ River Basin in 1973.
55
Figure 4.5 Land cover map of the Econ River Basin in 1995.
56
Figure 4.6 Land cover map of the Econ River Basin in 2004.
57
Table 4.4 Percentages of land cover over the Econ River basin.
Land Cover of the Econ River Basin
Year 1940's 1973 1995 2004
Wetland 33.2% 21.5% 25.9% 25.9%
Forest 3.0% 6.0% 3.9% 2.2%
Upland Non-Forested 58.6% 42.5% 25.8% 18.0%
Urban 0.2% 9.4% 22.6% 24.3%
Industrial 0.0% 1.4% 1.6% 2.3%
Recreational 0.0% 0.4% 1.0% 1.0%
Agricultural 2.6% 16.1% 12.6% 18.3%
Water 2.4% 2.0% 3.7% 4.4%
Transportation 0.0% 0.6% 3.1% 3.5%
As illustrated in the maps the urban population increases over time. There is a significant
increase in urban area between 1973 and 1995 which caused the upland non-forested area to
decrease significantly over time. There was a decrease in wetland area from 1940’s to 1973 and
then a slight increase from 1973 to 1995 and then maintained from 1995 to 2004. The decrease
from 1940’s to 1973 was most likely from development. The increase from 1973 to 1995 could
be from some wetland conservation that led to the formation of new wetlands or reclassified
areas to be wetlands that weren’t classified that way before. The forest area increased in 1973
and then decreased to 2004. The increase in forest area may be an artificial increase due to miss-
identification between wetland and forest area in the 1940’s. Due to the quality of the imagery it
58
was hard to differentiate forest and wetland. This could have lead to small amounts of miss-
identification.
Industrial, recreational & Transportation categories steadily increased overtime. This
increase was expected due to the increasing population and urban area. Agriculture increased
significantly from the 1940’s to 1973, then decrease in 1995 and again increased in 2004. The
increase in 1973 was most like due to the increased population and the need for more produce.
The decrease in 1995 and then increase in 2004 may be because farmers moving away from the
city to other areas because of freezes in the 1980’s and then returning years later.
The water area decreased from the 1940’s to 1973 and then steadily increased to 2004.
The decrease in water area may be an artificial decrease due to not having an entire map of the
1940’s. Since the water area is such a small portion, the percentage of water area may have been
slightly skewed by leaving out upland areas. The significant increase from 1973 to 2004 is most
likely because of increased channelization due to urbanization. The urbanization causes vast
areas to be paved and decreased infiltration into the soil. Since the runoff cannot infiltrate it is
directed into manmade ponds which then flow into the river. The increase in development
increases the number and sizes of the ponds thus causing the water area to increase.
4.3 Water Withdrawals
Many populated areas withdraw water from lakes, streams and groundwater to consume
or use for irrigation or other industries. Population growth in the Econ River basin points
towards increased groundwater pumping and water withdrawal. Much of the groundwater
59
pumped is from the Florida Aquifer that is deep underground. This encompasses many
watersheds, and fluctuations in this aquifer will most likely not affect the stream flow of the
Econ River. Shallow wells are used to pump water from the surficial aquifer. The surficial
aquifer is much more shallow than the Florida aquifer and is much more sensitive to short term
droughts and flooding. Base flow from the Econ River is largely a factor of the surficial aquifer
and its discharge.
Figure 4.7 Water withdrawal in Orange County over time.
0
50
100
150
200
250
300
350
1965 1970 1975 1980 1985 1990 1995 2000
Mill
ion
Gal
lon
s p
er
Day
Year
Water Withdrawal Orange County GW Surface Total
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Figure 4.8 Water withdrawal in Seminole County over time.
Figures 4.7 and 4.8 show the water withdrawal from Orange and Seminole Counties over
time. (http://water.usgs.gov/watuse/ ). In Orange County before 1975 surface water withdrawal
was slightly greater than ground water withdrawal. After 1975 ground water withdrawal is
significantly greater with an average pumping rate around 200 million gallons per day while
surface water withdrawal steadily decreased. In Seminole County the ground water withdrawal
was always greater than the surface water withdrawal. Like Orange County, Seminole County
had a significant growth in ground water pumping and surface water withdrawal declined to
become almost negligible.
The total pumping rate for each county grew over time showing an increase in population
growth. During population growth there are more people in a smaller area causing a greater
water demand. The water that is pumped out from the deep and shallow aquifers reduces the
groundwater available for streams and rivers to maintain water levels and flows. Land use and
land cover change also point towards increased pumping because of the landscaping water
0
20
40
60
80
100
1965 1970 1975 1980 1985 1990 1995 2000
Mill
ion
gal
lon
s p
er
day
Year
Water Withdrawal Seminole County GW Surface Total
61
demand. Landscaped areas need to be watered regularly. This water comes from potable water
and reclaimed water and also wells. Increasing population in the Econ River basin has changed
the land use and water demand which has in turn increased water withdrawals.
4.4 Effluent Discharge
Effluent discharge is a contributing factor to the Econ River and its flow regime. This
discharge from water treatment plants can increase low flows in the river and also decrease the
water quality. The Iron Bridge wastewater treatment plant (Iron Bridge WWTP for short) is a
regional facility located in the Econ River basin. See Figure 4.9 for its discharge locations in the
watershed. The Iron Bridge plant is owned by the City of Orlando but also serves Winter Park,
Maitland, Casselberry and unincorporated portions of Orange and Seminole Counties. The
facility was built in three phases. The first phase of the facility began operating in 1982 and was
designed to treat 24 mgd. The second phase began operating in 1989 and was designed to treat
12 mgd. The third phase began operation in 1991 and was designed to treat 12 mgd. After all
the phases were completed the facility had a total treatment capacity of 40 mgd.
62
Figure 4.9 Iron Bridge effluent discharge locations.
The Iron Bridge WWTP has two effluent discharge locations, the Little Econ River and
the man made Orlando Easterly Wetlands. The discharge limit for the Little Econ River is 28
mgd and the limit for the wetlands is 20 mgd. The Orlando Easterly Wetlands was originally
natural wetlands turned into cattle pasture and then transformed into manmade wetlands for the
Iron Bridge facility to discharge to. The wetlands are 1,250 acres located outside the Econ River
basin. The wetlands consist of bermed cells which the water flows through. The wetland began
receiving flows from the facility in 1987 ("Iron bridge regional,").
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Data was gathered from City of Orlando to determine the effluent discharge over time
into the Econ River. This data was plotted on Figure 4.10.
Figure.4.10 Effluent discharge from the Iron Bridge facility into the Econ River.
The average effluent discharge into the Econ River is 0.05 mm per day. The plot shows a few
peaks around 0.09 mm per day.
0
0.02
0.04
0.06
0.08
0.1
0.12
Jan
-95
Jul-
95
Jan
-96
Jul-
96
Jan
-97
Jul-
97
Jan
-98
Jul-
98
Jan
-99
Jul-
99
Jan
-00
Jul-
00
Jan
-01
Jul-
01
Jan
-02
Jul-
02
Jan
-03
Jul-
03
Jan
-04
Jul-
04
Jan
-05
Jul-
05Mill
ime
ters
pe
r d
ay (
mm
/d)
Time (Months)
Iron Bridge Effluent Discharge into the Econ River
Effluent Discharge
64
Figure 4.11 Effluent discharge into the Econ River plotted with the annual minimum flow of the
river.
Figure 4.11 shows the scale of the effluent discharge in relation to the annual low flow.
From the low flow data an average was taken from the first 10 years which equals 0.045 mm per
day. This number is the average minimum annual flow before significant human development.
A second average was taken from the last 10 years which equals 0.149 mm per day. This
number is the average minimum annual flow after significant human development. The
difference between the two averages is 0.104 mm which equals the net increase in annual
minimum flows between the two periods. Figure 4.11 shows an average effluent discharge into
the Econ River of about 0.05 mm per day. This accounts for nearly half of the increase in low
0
0.05
0.1
0.15
0.2
0.25
0.3
1936 1946 1956 1966 1976 1986 1996 2006
An
nu
al M
in Q
(m
m/d
ay)
Year
Econ Annual Low Flow
1936-1946 Average=0.045
1999-2009 Average=0.149
Effluent Discharge
65
flow into the river. Although the effluent discharge does not account for the total net increase it
accounts for a significant portion. The remainder of the increase in low flow is likely due to
storm water management regulations.
4.5 Stormwater Management Regulations
Development in Florida has caused the need for stormwater management to manage flood
waters and maintain the health of the water systems. Florida’s water management practices have
evolved over the years as researchers have improved their knowledge on what regulations work
best. In the beginning most water management was mainly about managing flood waters.
Channels and pipe networks were built to convey flood waters away from developments to
prevent flooding and damage to property. Declining water quality later caused the need for
management practices to improve and maintain the water bodies.
The Water Pollution Control Act of 1948 was the first water quality legislation. This law
established the framework in which states and the federal government would develop
cooperative programs. Later the Federal Water Pollution Control Act in 1956 and the Water
Quality Act of 1965 directed the states to develop their own water quality standards to
accommodate their specific water quality goals. In 1972 the Federal Water Pollution Control
Act Amendments also called the Clean Water Act created a National Pollutant Discharge
Elimination System (NPDES). This system requires each point source discharge to obtain a
permit. This system made water quality standards easier to enforce. ("Water quality standards,"
2012)
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In the late 70’s the St. John’s River Water Management District (SJRWMD) was
establishing itself and its water management needs. Before the late 70’s permits were handled
thorough the FDEP. The SJRWMD established its own permitting system and rules, requiring
developers to obtain permits through them.
Current SJRWMD regulations have different requirements for different types of
stormwater treatment systems. The following is a summary of some of the main criteria that is
applicable for this discussion. Refer to the SJRWMD Environmental Resource Permits:
Regulation of Stormwater Management Systems for all requirements. Retention systems require
off-line retention of the first one half inch of runoff or 1.25 inches of runoff from the impervious
area, whichever is greater. For on-line retention systems an additional one half inch of treatment
of runoff is required. If discharging into an impaired water body an additional 50% of volume is
required. Wet and dry detention systems require a treatment volume of the first one inch of
runoff or 2.5 inches of runoff volume from the impervious area, whichever is greater. It must be
designed so that the pond will bleed down one-half of the volume within 24-30 hours following a
storm event, but no more than one- half of this volume will be discharged within the first 24
hours. The system must contain a permanent pool volume to achieve a residence time of at least
14 days during the wet season (June-October). If discharging into an impaired water body an
additional 50% of volume is required. Dry detention systems must contain areas of standing
water for no longer than three days following a rainfall event.
The volumes of these systems are also controlled by the required attenuation. SJRWMD
requires that the pond attenuate the 25 year 24 hour storm and the mean annual 24 hour storm.
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This means that the post-development flow coming off the site must not exceed the pre-
development flow. The attenuation is designed to hold back stormwater to prevent flooding.
Attenuation requires most pond volumes to be increased because the increase in impervious
increases the amount of runoff coming from the site.
Developed sites and increased impervious areas require treatment ponds that provide for
treatment and attenuation. These ponds are different sizes and function differently depending on
the pre-development conditions, type of use, type of soil, elevations, etc. Stormwater ponds
collect the stormwater and release it gradually to prevent flooding. Systems attenuate the rate of
runoff from the site but not the total volume. The larger amount of impervious area in the post
development condition results in a larger amount of runoff because the runoff cannot infiltrate
into the soil as easily as the pre development condition. This additional amount of runoff is
released after the storm event through bleed down structures to bring the pond back to its normal
water level. The slow release of the additional stormwater after the storm event can increase the
low flows between storm events. This means the maximum flows will not increase because the
ponds are holding back the peak flows, but the minimum flow will increase because of the runoff
being released gradually after the storms.
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CHAPTER 5 : CONCLUSIONS AND FUTURE WORK
The Econ watershed is a dynamic watershed that has endured changes over time. This
thesis analyzes the hydrologic changes, climatic changes and human interferences of the Econ
watershed. Through this analysis hydrologic changes were determined to be a slight increase in
annual stream flow and a significant increase in low flow. These changes are the result of human
impacts on the watershed. Ground water levels in wells around the watershed were also
analyzed and showed a decrease around the areas with substantial land use change.
In order to look at all of the factors that can play a part in the hydrologic changes in the
watershed the climatic changes were analyzed. The annual precipitation had no uniform trend.
There was a slight increase in temperature but it does not appear to yield significant changes to
the watershed. The potential evaporation increased similarly to the temperature trend. This was
expected since the potential evaporation was calculated using the Hamond Method which uses
the temperature. Based on these results it was determined that there were significant changes in
the potential evaporation but no other significant changes to the climate over the study period.
Human interferences are the primary reason for the hydrologic changes in the watershed.
Population growth from the Greater Orlando area has resulted in significant land use change
since the 1970’s. This land use change has increased runoff by increasing the impervious area in
the watershed. Effluent discharge has also played a part in increasing the low flow of the Econ
River. The Iron Bridge facility is a large wastewater facility that discharges into the Econ River.
This discharge seems to play a significant role in the low flow event. Other changes to the
watershed are storm water management regulations. These regulations require developments to
69
capture runoff in ponds to increase water quality of runoff and decrease flooding. These systems
are also required to attenuate the flow off the site. This means peak runoff from the site is held
back to be released at a later time. When this runoff is released it is after the peak storm event
and can cause an increase in low flow. Human interferences such as effluent discharge, land use
change, and storm water management regulations have played a part in changing the hydrologic
cycle of the Econ River watershed.
This thesis showed a numerical analysis of the change in land use and the effluent
discharge into the Econ River. Future work should include a numerical analysis on the effects of
the stormwater management practices on the watershed. This analysis may include determining
the volumes of runoff over the watershed that is collected in storm water systems and a time
analysis on how the systems across the watershed hold back the runoff. Quantifying the effects
of the stormwater management practices will help to complete the overall water budget analysis
of the Econ River flow regime.
70
REFERENCES
[1] Brabham, Mary. Econlockhatchee River. St. Johns River Water Management District.
http://www.sjrwmd.com/middlestjohnsriver/econriver.html
[2] Brown, M., Luthin, C., Schaefer, J., Tucker, J., Hamann, R., Wayne, L., Dickinson, M.
(1990), Econlockhatchee River basin natural resources development and protection plan.
Vol I, II, III. Report to the St. Johns Water Management District.
[3] Iron bridge regional water pollution control facility. (n.d.). Retrieved from
http://www.cityoforlando.net/public_works/wastewater/reclaim.htm
[4] St. Johns River Water Management District, 2011. Land Use / Land Cover GIS data years
1973, 1995, 2004. Accessed February 21, 2011.
http://www.sjrwmd.com/gisdevelopment/docs/themes.html
[5] Sun, Ge, Steven G. McNulty, Jennifer A. Moore Myers, and Erika C. Cohen, 2008. Impacts
of Multiple Stresses on Water Demand and Supply Across the Southeastern United
States. Journal of the American Water Resources Association (JAWRA) 44(6):1441-
1457. DOI: 10.1111 ⁄ j.1752-1688.2008.00250.x
[6] Wang, D., and X. Cai (2010), Comparative study of climate and human impacts on seasonal
baseflow in urban and agricultural watersheds, Geophys. Res. Lett., 37, L06406,
doi:10.1029/2009GL041879.
[7] Wang, D., and X. Cai (2009), Detecting human interferences to low flows through base flow
recession analysis, Water Resour. Res., 45, W07426, doi:10.1029/2009WR007819.
[8] Wang, D., and M. Hejazi (2011), Quantifying the relative contribution of the climate and
direct human impacts on mean annual streamflow in the contiguous United States, Water
Resour. Res., 47, W00J12, doi:10.1029/2010WR010283.
[9] Wang, D., & Cai, X. (2010). Recession slope curve analysis under human
interferences. Advances in Water Resources, 33, 1053-1061. doi:
10.1016/j.advwatres.2010.06.010
[10] Water quality standards history. (2012, April 03). Retrieved from
http://water.epa.gov/scitech/swguidance/standards/history.cfm